Radiation therapy is an effective treatment option for men diagnosed with localized prostate cancer. This modality delivers high-energy rays, such as X-rays or protons, to damage the DNA of cancer cells, destroying their ability to divide and multiply. Advanced planning techniques minimize the radiation dose received by surrounding healthy tissues, such as the bladder and rectum. For many individuals with early-stage disease, radiation therapy serves as a primary treatment intended to eliminate the cancer entirely.
Types of Radiation Treatment
Radiation therapy encompasses two distinct delivery methods: external and internal. The choice depends on the cancer’s characteristics and the patient’s overall health profile.
External Beam Radiation Therapy (EBRT)
EBRT involves a machine outside the body that directs focused radiation beams toward the prostate. Modern EBRT often utilizes Intensity-Modulated Radiation Therapy (IMRT), which shapes the beams and modulates their intensity. This allows for a precise dose distribution that conforms to the tumor’s shape, reducing exposure to nearby healthy tissue. Treatment is typically delivered in daily sessions over several weeks, though newer approaches like Stereotactic Body Radiation Therapy (SBRT) deliver a higher dose per session over a much shorter course, sometimes in five or fewer days.
Brachytherapy
Brachytherapy is a form of internal radiation where the source is placed directly inside the prostate gland. Low-dose-rate (LDR) brachytherapy involves permanently implanting tiny radioactive seeds that release radiation slowly over several months. High-dose-rate (HDR) brachytherapy involves temporarily placing radioactive sources into the prostate for short, intense sessions before removal. Brachytherapy may be used alone for small, low-risk tumors or combined with EBRT for more aggressive disease.
Measuring Treatment Success
The effectiveness of radiation therapy is measured by tracking disease control and patient survival. For localized disease, the primary metric is Biochemical Recurrence-Free Survival (BRFS). BRFS is defined by the prostate-specific antigen (PSA) level remaining stable or falling after treatment, indicating the cancer has not returned. A rising PSA level following treatment is the first sign of potential failure, known as biochemical recurrence.
For men with low-risk localized prostate cancer, long-term BRFS rates are high. Ten-year BRFS rates are often reported around 85% with modern EBRT and approximately 90% with brachytherapy.
Overall Survival (OS) and Prostate Cancer-Specific Survival (PCSS) are also used to assess long-term outcomes. For patients with localized disease, 10-year PCSS rates following radiation therapy are excellent, often exceeding 97% for low and intermediate-risk categories. Even for high-risk localized disease, 10-year PCSS can be around 90%. These high rates confirm that radiation therapy is a highly curative option for many men.
Factors Affecting Outcomes
The effectiveness of radiation therapy is significantly influenced by specific characteristics of the tumor and the patient.
Tumor Stage and Risk Category
The initial stage of the cancer is a major determinant. Localized disease confined to the prostate responds much better than advanced disease that has spread outside the gland. Treatment success rates decline as the cancer progresses from low-risk to high-risk categories.
Gleason Score and Grade Group
The Gleason score and its corresponding Grade Group, which describe how abnormal the cancer cells look, are strong predictors of outcome. Higher Gleason scores (8 to 10) indicate a more aggressive cancer with a greater likelihood of recurrence. Patients with a Gleason score of 7 often have better outcomes when treated with higher radiation doses.
Pre-treatment PSA Levels
Pre-treatment PSA levels also play a substantial role in predicting efficacy. A lower PSA level before treatment is associated with a greater chance of long-term biochemical control. For example, studies show that for patients with a Gleason score of 7, 5-year BRFS rates drop dramatically from 83% (PSA below 10 ng/mL) to 21% (PSA of 20 ng/mL or higher). The patient’s overall health and ability to complete the full course of treatment also influence the final result.
Common Treatment Side Effects
The proximity of the prostate to the bladder and rectum means that side effects related to these organs are common.
Urinary Issues
Urinary issues are frequently experienced, often beginning during the treatment course. Symptoms include increased frequency and urgency of urination. Some men may develop radiation cystitis, an irritation of the bladder lining that can cause a burning sensation during urination.
Bowel Issues
Bowel-related side effects occur because the rectum is directly behind the prostate and receives some incidental radiation dose. Symptoms can include diarrhea, rectal irritation, and radiation proctitis. Most acute bowel issues resolve within a few weeks or months after treatment. However, a small percentage of men may experience long-term changes, such as persistent urgency or occasional rectal bleeding.
Sexual Function
Erectile dysfunction (ED) is a potential long-term side effect of radiation therapy. The onset of ED tends to be gradual, developing over months or years, unlike the more immediate effects often seen with surgery. Radiation can also cause a decrease in the volume of semen produced. These side effects vary depending on the type of radiation used and the patient’s sexual function before treatment.